The present invention is an improvement on the making biofilms systems disclosed in our patent U.S. Pat. No. 5,605,836 for MODULAR METHOD AND DEVICE FOR THE EVALUATION OF THE BIOCIDE TO PENETRATE BIOFILM incorporated herein by reference.
Biofilms caused by various kinds microbiological contamination occur frequently in the conveying system of food processing plants, implantable and insertable medical devices, airplane fuel tanks and pipeline filters, waste water discharge lines of nuclear power plant heat exchangers, pulp and paper industrial processes and so on. Such biofilms not only cause the affected pipelines to narrow, reducing their capacity and wasting energy but also could contribute to corrosion of the pipelines and endanger the entire system. In food and pulp processing plants, biofilms in conveying systems could additionally cause serious quality control problems. In hospitals, contaminated equipments and devices could infect patients. In aviation, once biofilms are developed in fuel lines, they could cause deterioration in the quality of the fuel and/or seriously affect air safety by damaging the integrity of the fuel lines by pitting the wall surface of the fuel lines so covered. Needless to say, how to overcome the problems caused by biofilns is a very important and pressing problem.
The effectiveness of these various biocides is expressed in terms of MIC—minimal inhibitory concentration. However, MIC is measured against microbiological concentrations in planktonic state only, and is quite irrelevant against microbes that have become sessile. It is not unusual to use biocides in concentrations of several hundred times, even thousand times the MIC to deal with sessile microbiological contamination. The main reason for this is that once biofilms are developed, they tend to act as barriers against the biocide. Indeed, many research results have already indicated that the use of MIC values to indicate biocide effectiveness is misleading, because the MIC values can't represent the actual effect of biocides on microorganisms that have developed biofilm.
In order to truly evaluate the effectiveness of a biocide against both planktonic and sessile microbes, a way must be developed to create biofilms of different thickness in the laboratory. At the present time, many different systems of biofilm reactors are being tested. For example, U.S. Pat. No. 6,361,963 to Smith et al. discloses a method and apparatus for determining the effect of various agents on the growth of biological material, microbially-influenced corrosion and the deposition of organic and inorganic contaminants. U.S. Pat. No. 6,410,256 to Ceri et al. discloses a method of making biofilms. U.S. Pat. No. 6,051,423 to Ceri et al. discloses bacteria are incubated to form a biofilm on projections by providing a flow of liquid growth medium across projections and an assay made of the resulting biofilm. U.S. Pat. No. 5,624,815 to Grant et al., U.S. Pat. No. 5,792,430 to Hamper and U.S. Pat. No. 4,753,775 to Ebersole et al. disclose the biological material in which the liquid sample is drawn over a solid support. McCoy et al. described the Robbins device in the Canadian Journal of Microbiology (1981), volume 27, p. 910 to 917. Ceri et al. described the Calgary biofilm device in the Journal of Clinical Microbiology (1999), volume 37, p. 1771 to 1776.
However, these systems are complicated, costly and time consuming to operate. More particularly, these devices and methods can't to make different thickness of biofilm rapidly.